Urinary and biliary stone disease afflicts more than 800,000 people in the US per year. Researchers have demonstrated the feasibility of fragmenting these stones endoscopically using a flashlamp pumped dye laser. These lasers are designed to operate over a broad spectrum and have not been optimized for the required parameters resulting in inefficient operation, frequent dye changes, and prohibitive costs. Fragmentation is optimized at 504nm but flashlamps are not optimized to pump dyes at this wavelength and green dyes do not exhibit good lifetime when compared to other dyes. The objective is to improve flashlamp efficiency by shifting the gas emission spectra into the blue region. The research proposed in this Phase I study is directed at a parametric evaluation of the effects of flashlamp gas composition, gas pressure, and flashlamp geometry on optical efficiency at 504nm. Dye life is to be studied through chemical modifications to dyes within the yellow and red spectrum to yield long life dyes lasing at 504nm.